The limitation of 1st law of thermodynamics is

Options

A. Energy can neither be created nor destroyed
B. Impossible to construct the `1^(st)` kind of perpetual motion machine
C. Law of conservation of energy
D. Spontaneous nature of a process

Answer

### Step-by-Step Solution:

1. **Understanding the First Law of Thermodynamics**:
The first law of thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another. This principle emphasizes the conservation of energy in physical and chemical processes.

2. **Identifying the Limitation**:
While the first law provides a framework for understanding energy conservation, it does not provide information about the direction of energy transfer or the spontaneity of processes. For example, it cannot predict whether heat will flow from a hot object to a cold one or vice versa.

3. **Example Illustration**:
Consider a cup of hot tea. According to the first law, the energy (heat) can be transferred to the surroundings, leading to a cooling of the tea. However, the first law does not prevent the hypothetical scenario where the tea absorbs heat from the surroundings to become hotter, which is not a spontaneous process.

4. **Spontaneity and Feasibility**:
The first law does not indicate which processes are spontaneous (i.e., occur naturally) and which are not. For instance, lifting water from a lower height to a higher height requires work input, and the first law does not explain why this process is not spontaneous without external energy.

5. **Conclusion**:
The limitation of the first law of thermodynamics is that it does not provide insights into the spontaneity of processes or the direction of energy flow. It only confirms that energy is conserved but does not dictate how or when that energy will be transferred or transformed.